Variable resistance control and switch with common operating member

ABSTRACT

An improved miniature variable resistance control and integral switch is provided for use in hearing aids. The combination is enclosed in a housing having an aperture in one end and an opening in the other end being closed by a base having terminals insert molded therein. The terminals are flush with the surface of the base whereby the resistance path supported on the surface is connected to the terminals by conductive material applied in a uniform layer directly on the surface and the terminals. A cavity in the base contains a switch contactor and switch contact in spaced parallel relationship. In order to actuate the switch and adjust the variable resistance control, a driver rotatably supported in the housing actuates a contactor for wipingly engaging the resistance path and actuates a switch actuator positioned between the switch contactor and the switch contact. The switch actuator and contactor are separated by the base and registered such that the switch is opened and closed when the variable resistance control is set at an extremely low resistance value. Electrical connection between a collector and the contactor is made through a conductive stop plate and wave washer disposed around the driver.

United states Patent [72] Inventors Ronald E. Bureham Arden, N.C.; William L. Kelver, Jr., Cassopolls, Mich. [2]] Appl. No. 35,859 [22] Filed May 8, I970 [45] Patented Dec-21,1971 [73] Assignee CTSCorporatlon Elkhnrt, Ind.

[54] VARIABLE RESISTANCE CONTROL AND SWITCH WITH COMMON OPERATING MEMBER 17 Claims, 3 Drawing Figs.

[52] U.S.Cl 338/198, 338/174, 338/172 [51] Int. Cl. I-IOIc 9/08 [50] Field otSenreh 338/160, 162, 163, 172, 174, 198, 200 [56] References Cited UNITED STATES PATENTS 2,929,040 3/1960 Barde'n 338/172 3,377,606 4/1968 Ferrel 338/174 (Ll-LL44.

2,791,666 5/1957 Daily Primary Examiner-Lewis H. Myers Assistant Examiner-Gerald P. Tolin Attorney-John J. Gaydos one end and an opening in the other end being closed by a base having terminals insert molded therein. The terminals are flush with the surface of the base whereby the resistance path supported on the surface is connected to the terminals by conductive material applied in a uniform layer directly on the surface and the terminals. A cavity in the base contains a switch contactor and switch contact in spaced parallel relationship. In order to actuate the switch and adjust the variable resistance control, a driver rotatably supported in the housing actuates a contactor for wipingly engaging the resistance path and actuates a switch actuator positioned between the switch contactor andthe switch contact. The switchactuator and contactor are separated by the base and registered such that the switch is opened and closed when the variable resistance control is set at an extremely low resistance value. Electrical connection between a collector and the contactoris made through a conductive stop plate and wave washer disposed around the'driver.

mama) new Ian 3629.780

FIGURE- 3 FIGURE- 2 INVENTORS. RONALD E. BURCHAM BY g fij A onus WILLIAM L. KELVER JR.

VARIABLE RESISTANCE CONTROL AND SWITCH WITH COMMON OPERATING MEMBER The present invention relates to electrical controls and, more particularly, to an improved variable resistance control and integral switch of the type employed in hearing aids and the like.

Various designs of hearing aids are available depending upon the particular requirements of the individual. One type mounts a complete hearing aid unit in one of the temples of a pair of spectacles while another is encapsulated into an ear mold and insertable into the inner semicircular canal of an car. In all of these designs it is desirable to utilize a construction which is not visible to the casual observer. Since the visibility of the hearing aid is largely dependent on the size of the hearing aid and the size of the several components making up the hearing aid, it is desirable to miniaturize the components of the hearing aid.

Due to the proximity of the hearing aid to the body, the hearing aid must operate in an environment containing dust, hair, hair oil, perspiration, and other foreign substances. The variable resistance control and switch is difficult to seal completely in a housing since the driver of the control must be connected to a rotatable knob extending outwardly of the housing for manual adjustment. Accordingly it would be desirable to provide an improved sealed variable resistance control and switch wherein the operation thereof is not affected by environmental conditions.

The particular requirements of manufacturers of hearing aids vary in that some manufacturers require a combined variable resistance control and switch whereas others merely require the variable resistance control. To minimize manufacturing costs it would be desirable to provide a construction wherein the variable resistance control and switch utilize the same basic structure such that, the control can be assembled with or without the switch.

In the fabrication of variable resistance controls it is always desirable to eliminate costly assembly procedures. In the past it has been found desirable to insert mold the terminals into a base which supports a resistance element having apertures for receiving the terminals. Ordinarily the terminals are positioned in the apertures in the resistance element with an end portion perpendicular to the surface of the resistance element. In order to electrically connect the end portions of the terminals to the resistance element a conductive epoxy is used. It is necessary to deposit a sufficient amount of conductive epoxy to fill the space between the terminals and the sidewalls of the apertures in order to provide a good electrical connection and eliminate possible movement of the resistance element relative to the terminals. In applying the conductive epoxy in this manner, the conductive epoxy often builds up at the apertures causing the contactor to raise up a considerable amount at the apertures. As the contactor is forced to raise up, the pressure on the contactor is increased resulting in an increased rate of wear of the contactor. Accordingly it would be desirable to eliminate the need for supporting a separate resistance element on a base having terminals insert molded therein and applying a nonuniform layer of conductive epoxy to terminals positioned in apertures in the resistance element.

Accordingly it is an object of the present invention to provide a new and improved variable resistance control and switch having the various desirable features set forth above. Another object of the present invention is to provide an improved variable resistance control and switch wherein the switch is so arranged with respect to the variable resistance control that it requires a minimum of space. An additional object of the present invention is to provide an improved variable resistance control and switch which provides a distinct feel when the switch is moved to the off position. A further object of the present invention is to provide a variable resistance control and switch wherein the structure is essentially sealed from environmental conditions and wherein the switch is basically self-cleaning to eliminate the affects of the presence of any possible foreign substances in the control. Still another object of the present invention is to provide an improved variable resistance control and switch wherein the resistive path is electrically connected to the terminals by a uniform layer of conductive material deposited directly onto the base and terminals insert molded into the base and having portions flush with the surface of the base supporting the resistive path. Yet another object of the present invention is to provide an improved variable resistance control and switch wherein the switch is fabricated so as to be electrically quiet during adjustment of the variable resistance control. Further objects and advantages of the present invention will be apparent as the following description proceeds and the features of novelty characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

Briefly the present invention is concerned with a variable resistance control adapted for combination with a switch comprising a housing having an aperture in one end and an opening in the other end. A base having terminals insert molded therein closes the opening in the other end of the base. The base is provided with an aperture in alignment with the aperture in the one end of the housing and a resistive path is supported on the base in electrical connection with the terminals. A driver is rotatably supported in the aperture in one end of the housing and in the aperture in the base. Where it is desired to combine the variable resistance control with a switch, the underside of the base is provided with a switch contactor and switch contact in spaced parallel relationship. A suitable insulating switch cam is rotatably supported by the driver and upon a predetermined motion of the driver the switch cam physically comes between the switch contactor and contact to open the switch. A collector terminal enters the control between the base and housing and is disposed about the aperture in one end of the housing. A contactor supported for wipingly engaging the collector terminal and the resistive path upon rotation of the driver is disposed between the collector terminal and the resistive path. Electrical connection is made between the collector and the contactor through a conductive stop plate and wave washer.

For a better understanding of the present invention reference may be had to the accompanying drawings wherein the same reference numerals have been applied to like parts and wherein FIG. 1 is an isometric view of a sealed variable resistance control and switch built in accord with the present invention;

FIG. 2 is a sectional view taken along line ll-ll of FIG. I; and

FIG. 3 is an exploded view of the control of FIG. 1.

Referring now to the drawings and specifically FIG. I there is illustrated an improved variable resistance control and switch generally indicated at 10 comprising a housing II, a base assembly 12 and a rotatable knob 13.

Considering first the housing 11, it comprises a cup-shaped member having a cylindrical wall 14 and an end wall 15 preferably molded of any suitable nonconductive material such as one of the phenolics. The end wall 15 is provided with an aperture 16 therein. Rotatable means in the form of a pivot stud or driver 18 rotatably supported in the aperture 16 has a flange 19 in bearing engagement with the end wall 15. The driver 18 is provided with a plurality of stepped shouldered portions 21, 22, 23 and 24. A collector terminal 26 disposed about the aperture 16 adjacent the shouldered portion 21 of driver 18 has a leg 27 extending downwardly along the cylindrical wall 14 of the housing 11 making a right angle and extending radially outwardly from the housing 11 for connection to an electrical circuit. A wave washer 28 encircles the shouldered portion 21 and bears against the collector terminal 26. According to the present invention the wave washer 28 is a thin substantially ring-shaped washer formed of a resilient conductive material and slightly bowed from a flat plane as shown exaggerated at 28a in FIG. 3. When the washer is compressed toward a flat position, the tendency of the resilient material to revert back to its original position produces a compressive force resisting the compression. A stop plate 29 and a contactor 30 are provided with keyed apertures 29a, 30a corresponding to the cross section of shouldered portion 22 and assembled with shouldered portion 22 disposed in the keyed apertures 29a, 30a in order to provide rotation of these parts vupon rotation of the driver 18. During assembly the stop plate 29 is positioned against the shouldered portion 21 compressing the wave washer 28 against the collector terminal 26 with a predetermined force. The shouldered portion 22 is flared outwardly over the contactor 30 at 22a to hold the contactor 30 and stop plate 29 against the shouldered portion 21 and secure the driver 18, the housing 11, and the collector terminal 26 in assembled relationship. Compression of the wave washer 28 provides the desired torque required for preventing accidental relative rotation between the driver 18 and the housing 11. In some applications the collector terminal 26 is bowed to provide the desired torque and the wave washer 28 is omitted. Due to the varying requirements for torque, however, it is desirable to utilize the wave washer 28, since the desired torque can be obtained by the selection of a specific wave washer made of a specific material and thickness. The stop plate 29 is provided with a radially extending arm 31 positioned in an interference path with a stop 17 projecting'radially inwardly from the cylindrical wall 14 of the housing 11. Since the wave-washer 28 must be compressed by a flat surface to provide a uniform compressive force, the stop plate 29 serves a dual purpose of providing the flat surface and stopping relative rotation of the driver 18 in the housing 11. In order to provide a conductive path between the collector terminal 26 and the contactor 30, the stop plate 29 and the wave washer 28 are fabricated from suitable conductive materials. Use of a conductive material for the stop plate 29 increases the strength of the stop plate 29 and accordingly increases the ability of the stop 17 and stop plate 29 to withstand rotational force.

The housing 11 is open at the end opposite end wall and the base assembly 12 is disposed in this opening. As best shown in FIG. 2 the base assembly 12 comprises a substantially cup-shaped base 32 formed with a flat surface 33 and a cylindrical skirt 34 forming a shoulder 35. The shoulder 35 engages the cylindrical wall 14 of the housing 11 and is provided with a notch 36 permitting clearance for the leg'27 of the collector 26. The base 32 may be secured to the housing 11 by any suitable method such as gluing or ultrasonic welding. In order to prevent accidental wobbling of the driver 18, the base 32 is provided with an aperture 37 in alignment with the aperture 16 in the end wall 15 such that the driver 18 is rotatably supported in both apertures. A resistance material 38 is deposited on surface 33 to form an arcuate resistance path about the aperture 37. The resistance path is provided at its end portions with conductive pads or hopoffs 39. As shown in FIG. 2 terminals 40, only one of which is shown, extend outwardly from the bottom of the base 32 and pass through the base 32 with end portions thereof being parallel to the surface 33 of the base 32. A surface of each of the terminals 40 is flush with surface 33 of the base 32. The terminals 40 are preferably insert molded into the base 32 to accurately position the terminals 40. To position the terminals properly in a mold cavity it is preferable that the terminals 40 be secured to a not shown terminal carrier strip. The terminal carrier strip is blanked out with groups of properly spaced terminals 40 and has apertures therein so that locating pins can be used to precisely position the terminals in the base 32. After the base 32 is molded to the terminals 40, the terminals 40 are severed from the terminal carrier strip. The conductive pads 39 are applied directly onto the base 32 and the terminals 40. The contactor 30 is positioned to wipingly engage the resistance path upon rotation of the driver 18.

As shown in FIG. 2 the cylindrical skirt 34 and the bottom of the base 32 define a cavity 41 in the base 32. Where it is desired to utilize a switch in combination with the variable resistance control, a switch contactor 42 is force-fitted into the cavity 41 with protrusions 42a on the switch contactor 42 being forced into the sides of the cavity 41 provided in the base 32 to secure the switch contactor 42 thereto. A switch actuator 43 of suitable insulating material having an aperture 44 corresponding to the cross section of the shouldered portion 24 of the driver 18, such that the switch actuator 43 is secured to the driver 18 for rotation therewith, is provided with a radially extending cam 45. A switch contact 46 is also force-fitted into the cavity 41 and provided with a terminal 47 extending outwardly from the control for connection to an electrical circuit. According to the present invention the switch contactor 42 has a resilient finger 42c biasing a switch contact 42d into engagement with the switch contact 46. Both the switch contactor 42 and the switch contact 46 are disposed about the driver 18 and lie in spaced parallel planes. Since the switch actuator 43 is positioned between the switch contactor 42 and switch contact 46 rotation of the switch actuator 43 will cause the cam 45 to rotate in an interference path with the switch contact 42d. Upon approaching the switch contact 42d the cam 45 first engages the resilient finger 42c whereupon additional rotation forces the resilient finger 42c away from the switch contact 46 thereby causing attached switch contact 42d to separate from switch contact 46 breaking the electrical connection. A predetermined further rotation positions the cam 45 between the switch contact 42d and the switch contact 46 at the same time the arm 31 on the stop plate 29 abuts against the stop 17. Once the cam 45 is positioned between the two switch contacts 42d, 46, a stable relationship exists since the resilient force of finger 42c is directed solely toward the switch contact 46 thereby increasing the frictional force required to be overcome in order to move the cam 45 from between the two switch contacts 42d, 46. In hearing aids it is desirable to actuate the switchwhen the volume is at its low point so that the user is not subjected to a sudden increase in volume. The present invention provides this feature by registering the contactor 30 and the switch actuator 43 on the same driver 18 and positioning the switch contact 42d in a position directly in alignment with one of the conductive pads 39 at the end of the resistance path. Selection of the conductive pad 39 for alignment with the contact 42d depends on whether clockwise or counterclockwise rotation is desired. Notches 340, only one of which is shown, are provided in the cylindrical skirt 34 to position the terminals 42b, 47 in proper position for aligning the contact 42d. Thus the cylindrical skirt 34 houses the switch assembly and accurately positions the switch contact 42d relative to the resistance path. In order to provide electrical clearance for the terminal 42b connected to the switch contactor 42, the switch contact 46 is provided with an arcuate portion 48. A suitable insulating disc 49 covers the cavity 41 to prevent dust and other materials from entering. The disc 49 can be secured in any suitable manner such as by gluing or by ultrasonic welding.

Once the driver 18, the housing 11, the base assembly 12, and the disc 49 are fastened together in assembled relationship, the assembly provides a tortuous path for any foreign material seeking ingress into the interior of the control 10. As best shown in FIG. 2 the material would first have to pass between the housing 11 and the rotatable knob 13 and then pass through the seal formed by the bearing engagement of flange 19 and end wall 15.

Since only the switch actuator 43 is rotated upon rotation of the driver 18, the switch contactor 42 and switch contact 46 remain in a fixed relative relationship once the switch is closed. Thus the switch will be electrically quiet during adjustment of the variable resistance control due to the absence of relative movement between the switch contactor 42 and the switch contact 46. It will be appreciated that even if foreign particles were to enter into the cavity 41 they would not interfere with the operation of the switch since the cam 45 wipes the contact 42d and the surface of the contact 46 as the switch is opened and closed such that any foreign particles would be removed from the surfaces thereof prior to their engagement. Indication that the switch is open is provided by the increased torque required to rotate the switch actuator 43 to a position wherein the radially extending cam 45 separates switch contact 42d from switch contact 36. The stop 'member 17 prevents additional rotation once the switch actuator 43 has opened the switch.

In order to facilitate rotation of the driver 18, the knob 13 is preferably insert molded with a washer 52 having a noncircular aperture corresponding to the cross section of the head of driver 18 such that rotation of the knob 13 will rotate the driver 18. A screw 53 secures the knob 13 to the driver 18 a decorative cap 54 may be suitably secured to the knob 13. This arrangement makes it possible to use a variety of knobs without materially adding to the cost of the control.

The above structural arrangement of parts has made it possible to provide a variable resistor and switch having a diameter exclusive of terminals and knob of 0.170 inch and a thickness including the knob and decorative cap of 0.143 inch. The structural arrangement also provides for ease in assembly since all but the knob 13, the screw 53, and the cap 54 can be secured from the same direction thereby permitting adaptation for mechanized assembly.

While there has been illustrated and described what is at present considered to be a preferred embodiment of the present invention,- it will be appreciated that numerous changes and modifications are likely to occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is: s I

l. The combination of a variable resistance control and an off-on switch comprising a molded base having a cavity therein, a resistance path supported on said base, a driver supported for rotation relative to the base, a contactor constrained to rotate upon rotation of said driver, said contactor being mounted for wipingly engaging the resistance path upon rotation of said driver, a switch contact disposed in said cavity, a switch contactor disposed in said cavity, and an insulative switch cam constrained to rotate relative to said switch contact and said switch contactor upon rotation of the driver, said switch contactor being biased into engagement with said switch contact, whereby said cam wipingly engages and separates said switch contact and said switch contactor upon a predetermined rotation of said driver.

2. The combination of claim I wherein said base electrically insulates said resistance path from said switch contactor.

3. The combination of claim 1 wherein said base is provided with an aperture extending therethrough, said driver being rotatably supported in said aperture.

4. The combination of claim 3 wherein said driver extends into said cavity and said switch cam is secured to said driver.

5. The combination of claim 1 wherein said switch cam wipes said switch contact and said switch contactor upon separating said switch contact from said switch contactor.

6. A variable resistance control comprising a housing, said housing having an aperture in one end and an opening in the other end, a base closing said opening in the other end, a resistance path supported on said base, said base being provided with an aperture in alignment with the aperture in said one end, a collector terminal spaced from said resistance path and disposed about said aperture in said one end, rotatable means supported in said aperture in said one end and in the aperture in said base, and a contactor constrained to move relative to the resistance path upon rotation of said rotatable means, said contactor wipingly engaging said resistance path upon rotation of said rotatable means while being electrically connected to said collector terminal.

7. The variable resistance control of claim 6 wherein said base is provided with a cavity adapted to house an off-on switch, and said driver passes through the aperture in said base into said cavity, said driver being adapted to actuate said switch.

8. The variable resistance control of claim 6 wherein said base is provided with end terminals molded therein, said end terminals having end ort ions parallel to a surface of said base, said end portions avtng a surface flush with the surface of said base, and conductive material deposited directly on said surface of said end portions electrically connects said end terminals and said resistance path.

9. The variable resistance control of claim 6 wherein a stop plate is disposed between said contactor and said collector terminal, and a stop projects from said housing in an interference path with said stop plate.

10. The variable resistance control of claim 9 wherein a wave washer separates said collector terminal from said stop plate and provides a desired rotational torque for said rotational means, said stop plate and said wave washer electrically connecting said contactor to said collector terminal.

11. The variable resistance control of claim 6 wherein resilient means provides the desired torque required for preventing accidental relative rotation between the rotatable means and the housing.

12. The variable resistance control of claim 11 wherein said resilient means comprises a wave washer disposed between said contactor and said collector.

13. The variable resistance control of claim 8 wherein said conductive material is bonded to the resistive path and to the end terminals, and said resistive path comprises a resistance material deposited as a film directly on'the surface of said base.

14. The variable resistance control of claim 11 wherein said resilient means is movable relative to said contactor.

15. A variable resistance control comprising a housing, said housing having an aperture in one end, a resistance path disposed in the other end of the housing, a collector terminal in spaced relationship to said resistance path and disposed around said aperture in said one end, rotatable means supported in said aperture in said one end, resilient means biasing the rotatable means toward the'one end of the housing and rotatable relative to said rotatable means, and a contactor constrained to rotate with said rotatable means, said contactor wipingly engaging said resistance path intermediate the ends thereof upon rotation of said rotatable means while being electrically connected to said collector terminal.

16. The variable resistance control of claim 15 wherein said collector terminal is'disposed flatwise against said one end of the housing and the resilient means electrically connects the contactor to the collector terminal.

17. The variable resistance control of claim 16 wherein a stop plate is disposed between said contactor and said collector terminal, and a stop projects from said housing in an interference path with said stop plate. 

1. The combination of a variable resistance control and an offon switch comprising a molded base having a cavity therein, a resistance path supported on said base, a driver supported for rotation relative to the base, a contactor constrained to rotate upon rotation of said driver, said contactor being mounted for wipingly engaging the resistance path upon rotation of said driver, a switch contact disposed in said cavity, a switch contactor disposed in said cavity, and an insulative switch cam constrained to rotate relative to said switch contact and said switch contactor upon rotation of the driver, said switch contactor being biased into engagement with said switch contact, whereby said cam wipingly engages and separates said switch contact and said switch contactor upon a predetermined rotation of said driver.
 2. The combination of claim 1 wherein said base electrically insulates said resistance path from said switch contactor.
 3. The combination of claim 1 wherein said base is provided with an aperture extending therethrough, said driver being rotatably supported in said aperture.
 4. The combination of claim 3 wherein said driver extends into said cavity and said switch cam is secured to said driver.
 5. The combination of claim 1 wherein said switch cam wipes said switch contact and said switch contactor upon separating said switch contact from said switch contactor.
 6. A variable resistance control comprising a housing, said housing having an aperture in one end and an opening in the other end, a base closing said opening in the other end, a resistance path supported on said base, said base being provided with an aperture in alignment with the aperture in said one end, a collector terminal spaced from said resistance path and disposed about said aperture in said one end, rotatable means supported in said aperture in said one end and in the aperture in said base, and a contactor constrained to move relative to the resistance path upon rotation of said rotatable means, said contactor wipingly engaging said resistance path upon rotation of said rotatable means while being electrically connected to said collector terminal.
 7. The variable resistance control of claim 6 wherein said base is provided with a cavity adapted to house an off-on switch, and said driver passes through the aperture in said base into said cavity, said driver being adapted to actuate said switch.
 8. The variable resistance control of claim 6 wherein said base is provided with end terminals molded therein, said end terminals having end portions parallel to a surface of said base, said end portions having a surface flush with the surface of said base, and conductive material deposited directly on said surface of said end portions electrically connects said end terminals and said resistance path.
 9. The variable resistance control of claim 6 wherein a stop plate is disposed between said contactor and said collector terminal, and a stop projects from said housing in an interference path with said stop plate.
 10. The variable resistance control of claim 9 wherein a wave washer separates said collector terminal from said stop plate and provideS a desired rotational torque for said rotational means, said stop plate and said wave washer electrically connecting said contactor to said collector terminal.
 11. The variable resistance control of claim 6 wherein resilient means provides the desired torque required for preventing accidental relative rotation between the rotatable means and the housing.
 12. The variable resistance control of claim 11 wherein said resilient means comprises a wave washer disposed between said contactor and said collector.
 13. The variable resistance control of claim 8 wherein said conductive material is bonded to the resistive path and to the end terminals, and said resistive path comprises a resistance material deposited as a film directly on the surface of said base.
 14. The variable resistance control of claim 11 wherein said resilient means is movable relative to said contactor.
 15. A variable resistance control comprising a housing, said housing having an aperture in one end, a resistance path disposed in the other end of the housing, a collector terminal in spaced relationship to said resistance path and disposed around said aperture in said one end, rotatable means supported in said aperture in said one end, resilient means biasing the rotatable means toward the one end of the housing and rotatable relative to said rotatable means, and a contactor constrained to rotate with said rotatable means, said contactor wipingly engaging said resistance path intermediate the ends thereof upon rotation of said rotatable means while being electrically connected to said collector terminal.
 16. The variable resistance control of claim 15 wherein said collector terminal is disposed flatwise against said one end of the housing and the resilient means electrically connects the contactor to the collector terminal.
 17. The variable resistance control of claim 16 wherein a stop plate is disposed between said contactor and said collector terminal, and a stop projects from said housing in an interference path with said stop plate. 